Laser light generating apparatus

Abstract

An object of the invention is to provide a laser light generating apparatus capable of minimizing loss in a resonator to give a high efficiency of wavelength conversion. A resonator comprises two reflecting mirrors 1 and 2 arranged in linear relationship and a non-linear optical crystal 3 disposed in the resonator. The non-linear optical crystal 3 is formed in a trapezoid shape so that a pair of input and output sides opposite to each other are tilted with respect to the optical propagation axis. The fundamental laser light is introduced along the optical propagation axis into the optical resonator, converted to a second harmonic by the non-linear crystal 3, and released outside from the reflecting mirror 2. It is made possible to adjust the beam diameter and convergence angle of the laser light on the light incidence plane(Y-Z plane) when the laser light passes the input and output sides of the non-linear optical crystal 3. For example, the incident plane is made to be consistent with a plane where the acceptance angle of the non-linear optical crystal 3 is limited to a small degree, thus increasing the efficiency of wavelength conversion.

What is claimed is: 
     
       1. A laser light generating apparatus comprising: an optical resonator having at least a pair of reflecting means; and   a non-linear optical crystal disposed in the optical resonator, the apparatus for introducing fundamental laser light to the optical resonator to cause a resonance action of the fundamental laser light to produce laser light whose wavelength is converted by the non-linear optical crystal, wherein the non-linear optical crystal has a pair of input and output sides which are arranged opposite to and not parallel to each other and also, tilted with respect to an optical propagation axis, the fundamental laser light incident in the non-linear optical crystal being set so that a beam waist is formed to have an oval shaped cross section and that a plane including the incident direction of the fundamental laser light and the direction of the normal to the input and output sides of the non-linear optical crystal and a direction, where the acceptance angle for phase matching in the non-linear optical crystal is small, are substantially parallel.   
     
     
       2. A laser light generating apparatus comprising: an optical resonator having at least a pair of reflecting means and a combination of a non-linear optical crystal; and   a laser medium disposed in the optical resonator, the apparatus for introducing exciting light for exciting the laser medium from outside to the optical resonator to generate fundamental laser light in the optical resonator by the laser medium, and further generate laser light whose wavelength is converted by the non-linear optical crystal, wherein the non-linear optical crystal has a pair of input and output sides which are arranged opposite to and not parallel to each other and tilted with respect to the optical propagation axis, the fundamental laser light incident in the non-linear optical crystal being set so that a beam waist is formed to have an oval shaped cross section and that a plane including the incident direction of the fundamental laser light and the direction of the normal to the input and output sides of the non-linear optical crystal and a direction, where the acceptance angle for phase matching in the non-linear optical crystal is small, are substantially parallel.   
     
     
       3. The laser light generating apparatus of claim 1 or 2 wherein the fundamental laser light is a linearly polarized light which is polarized normally to the plane including the incident direction of the fundamental laser light and the direction of the normal to input and output sides of the non-linear optical crystal. 
     
     
       4. The laser light generating apparatus of any one of claims 1 through 2, wherein the optical resonator is a folded resonator in which the incident direction is consistent with the reflecting direction on the reflecting means. 
     
     
       5. The laser light generating apparatus of any one of claims 1 through 2, wherein the optical resonator is a ring resonator in which the incident direction is not consistent with the reflecting direction on the reflecting means. 
     
     
       6. The laser light generating apparatus of claims 5, wherein the optical resonator is a ring resonator in which the fundamental laser light is incident at an oblique angle to input and output sides of the non-linear optical crystal so as to correct its astigmatism. 
     
     
       7. The laser light generating means of any one of claims 1 through 2, wherein the optical resonator is a ring resonator which has a first optical propagation axis extending across the non-linear optical crystal and a second optical propagation axis extending not across the same, both the axes are provided between the first and second reflecting means. 
     
     
       8. The laser light generating apparatus of claim 7, wherein the optical resonator is a ring resonator in which the fundamental laser light is incident at an oblique angle to input the output sides of the non-linear optical crystal so as to correct its astigmatism. 
     
     
       9. The laser light generating apparatus of any one of claims 1 or 2, wherein the non-linear optical crystal is of C 5  L 1  B 6  O 10  (cesium lithium borate). 
     
     
       10. The laser light generating apparatus of any one of claims 1 or 2, wherein the non-linear optical crystal is of BBO (beta-barium borate).